1. The Field of the Invention
This invention relates to jacking apparatus for moving a heavy load along a rail.
2. The Prior Art
Many types of jacking arrangements have been used and proposed for moving heavy loads along a rail or track. A rack is often attached to the rail, and a pair of cars, each carrying a dog, pawl or latch for engagement with the teeth of the rack, are slidably mounted on the rail. Reciprocal motion with respect to each other is imparted to the cars with selective engagement of the dogs, pawls or latches with the rack teeth, to cause progressive, incremental travel of the cars along the rail to move a load attached to one of them.
Such arrangements, however, are not well adapted for moving loads that are bi-directional. They do not ordinarily provide efficient moving of surging loads, for example, encountered in lifting pipe or jacket loads on a barge which may itself be subject to rising and falling wave action.